This invention relates to sputter-etching device utilizing radio-frequency discharge.
For instance in a vacuum evaporation process, sputter-etching is carried out in order to clean a surface to be vacuum-evaporated.
A conventional sputter-etching device of this type is as shown in FIG. 1. A flat-plate-shaped electrode 2 is placed in a vacuum chamber 1. An object 3 to be processed is put on the electrode 2. Radio-frequency discharge is then effected between the electrode 2 and the vacuum chamber 1, so that gas ions such as argon ions are formed in the vacuum chamber 1 by the utilization of the rectification action of the discharge, to subject the object 3 to sputter-etching.
The flat-plate-shaped electrode 2 is electrically insulated by insulating members 4 from the vacuum chamber 1, and is surrounded by a dark space shield 5. The electrode 2 is connected to a radio-frequency power source 10 through a circuit made up of a direct current blocking capacitor 6, a matching coil 7 and a matching capacitor 8, and through a radio-frequency cable 9. The device further comprises a shield 11 for preventing a radio-frequency leakage from the circuitry. The gas in a gas cylinder 12 is supplied through a needle valve 13 into the vacuum chamber 1.
When the radio-frequency discharge is effected in the device, the gas in the vacuum chamber 1 is ionized. The gas ions impinge on the flat-plate-shaped electrode 2; that is, the gas ions sputter the surface of the object 3 to be processed, so that the surface of the object 3 is cleaned.
However, the conventional device suffers from the following drawbacks:
One of the drawbacks is that, upon sputtering, the surface material of the object 3 is scattered around to stick to the inner wall of the vacuum chamber 1. Therefore, it is necessary to clean the vacuum chamber 1; however, it is considerably troublesome and difficult to clean the vacuum chamber, because the latter must be handled with great care. In addition, in the case where a sputter-etching device and a sputtering device are juxtaposed, i.e. a device is so formed that a sputter-etching process and a sputtering process are carried out in succession, it is necessary to segregate the sputter-etching section of the device from the sputtering section.
A second drawback is that the device suffers from an end effect. An etching rate is high at the ends of the flat-plate-shaped electrode 2, while it is low at the central portion of the electrode 2, as shown in FIG. 2. As is apparent from FIG. 2, in each end portion of the electrode 2 the etching rate is greatly changed even if the electrode position is changed only slightly; and on the other hand, the etching rate is considerably low in the central portion of the electrode where the etching rate is constant. Since it is necessary that the entire surface of an object to be processed is uniformly etched, the central portion of the electrode is used in the etching process; however, this method is undoubtedly low in efficiency.
A third drawback is that it is difficult to carrying out the etching process while an object to be processed is being moved, i.e. it is considerably difficult to move the electrode 2 on which the object is placed.